Briefly, and basically, the self-contained controller of the invention maintains constant low flow rates of fluids regardless of downstream pressure or pressure changes, incorporating a metering valve as an integral part of the controller and, preferably, includes a direct read dial flow indicator. The controller discharges liquids at a fixed high pressure greater than the downstream pressure and allows continuous non-pulsive flow even from piston or diaphragm type pumps.
Existing differential pressure regulation devices, such as the Moore Model Series 63DL, manufactured by Moore Products Co. of Spring House, Pa., and similar devices by other manufacturers, are designed for relatively low pressure and high flow rate applications (generally in the range of 30-210 gallons per hour). When these units are used for extremely low flow rates (0.005-10.0 gallons per hour), problems are encountered. Extremely high velocities are produced within the pressure regulation device, causing associated erosion of seat material and extreme chemical or fluid shear. Such problems have been found to lead to inaccurate metering, an inability to operate at extremely low flow rates, and shortened useful life of the unit due to deterioration of the valve seat.